Native Americans as active and passive promoters of mast and fruit trees in the eastern USA

We reviewed literature in the fields of anthropology, archaeology, ethnobotany, palynology and ecology to try to determine the impacts of Native Americans as active and passive promoters of mast (nuts and acorns) and fruit trees prior to European settlement. Mast was a critical resource for carbohydrates and fat calories and at least 30 tree species and genera were used in the diet of Native Americans, the most important being oak (Quercus), hickory (Carya) and chestnut (Castanea), which dominated much of the eastern forest, and walnut (Juglans) to a lesser extent. Fleshy tree fruits were most accessible in human-disturbed landscapes, and at least 20 fruit- and berry-producing trees were commonly utilized by Native Americans. They regularly used fire and tree girdling as management tools for a multitude of purposes, including land clearing, promotion of favoured mast and fruit trees, vegetation control and pasturage for big-game animals. This latter point also applies to the vast fire-maintained prairie region further west. Native Americans were a much more important ignition source than lightning throughout the eastern USA, except for the extreme Southeast. First-hand accounts often mention mast and fruit trees or orchards in the immediate vicinity of Native American villages and suggest that these trees existed as a direct result of Indian management, including cultivation and planting. We conclude that Native American land-use practices not only had a profound effect on promoting mast and fruit trees but also on the entire historical development of the eastern oak and pine forests, savannas and tall-grass prairies. Although significant climatic change occurred during the Holocene, including the 'Mediaeval Warming Period' and the 'Little Ice Age', we attribute the multimillennia domination of the eastern biome by prairie grasses, berry-producing shrubs and/or mast trees primarily to regular burning and other forms of management by Indians to meet their gastronomic needs. Otherwise, drier prairie and open woodlands would have converted to closed-canopy forests and more mesic mast trees would have succeeded to more shade-tolerant, fireQ sensitive trees that are a significantly inferior dietary resource.